The overall goal of the proposed research is to gain further knowledge of the physiology and pharmacology of aqueous outflow in the human eye. A major emphasis in the proposed studies is to characterize the role of cAMP in mediating changes in outflow facility, with an overall hypothesis that there is probably more than one cyclase involved in mediating the responsiveness of the outflow system to such diverse stimuli as epinephrine, prostaglandins, muscarinic agonists and modulators of Na/K/2Cl co-transport. The specific aims include: (1) identification of isoforms of adenylate cyclase in human outflow tissue and pharmacological characterization of cAMP-mediated outflow in human outflow tissue; (2) pharmacological characterization of the outflow facility increasing-effect of muscarinics which occurs directly on human outflow tissue in vitro and is independent of the ciliary muscle, and mapping of the subtypes of muscarinic receptors in the outflow pathways; and (3) pharmacological characterization and identification of isoforms of the endothelial-like Na/K/2Cl co-transport system which has recently been described in outflow tissue. The proposed studies will make use of physiological, biochemical and molecular biological methods in providing a more complete understanding of the regulation of aqueous outflow in the human eye. Enhanced understanding of the basic mechanisms underlying normal outflow may lend insight into the pathogenesis of primary open angle glaucoma and facilitate development of improved treatments.